Engine light on 97 4.6L F150 is driving me crazy! EGR...

My "check engine" light on my 97 4.6L f150 is driving me nuts! The light came on a while back, but the truck runs fine and gas mileage hasn't suffered. I finally had Auto Zone put a computer on it and the code came up EGR "insufficient flow". I bought a new EGR valve and reset the light. Back on in a couple days. Then I got this bright idea that a real "repair shop" may have a better computer that could pinpoint the problem. At least they said it was better. (I don't believe it). Anyhow, they told me to replace the PFTE or whatever its called and another vaccum control valve or somwthing like that. Im probably not calling them by their correct name, but its a small silver box with some sort of computer card in it that costs about $90, and another part that has a small filter on the top of it and costs around $30. the guy at the Ford place said this is pretty much all of the EGR stuff that goes bad.

Well, the light went off for about 10 months. Now its on again, right when I'm about to sell the truck. I figured my cheapo Auto Zone EGR valve was bad, so I headed back to Auto Zone to diagnose it again. Its thae same old code, bad EGR flow. I replaced the EGR valve with a factory Ford one (only $55 bucks, believe it or not!). Light came back on. Oh well, I guess my PFTE (the silver box) from Car Quest must be bad. I went to buy another one and the guy was cool and gave me a new one without me even asking! Light came back on. I havent changed the third part yet (I had earlier replaced this with a genuine Ford part).

I have to think that something else is causing the bad code. I am running out of time, patience, and money!! Any ideas? The truck is still running fine and getting normal mileage. If I disconnect the bettery to reset the light it may stay off for an hour, or three days.

I am just about at my wits end, and am ready to just disconnect the engine light altogether. Is there an easy way to do this if I have to?

thanks in advance

Reply to
rgdavico
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I'm not that familiar with this EGR system, but it seems to me like there may be some kind of restriction in the system that could be blocking the flow. Has anyone actually looked at the data the computer is seeing on the scan tool to see what's going on? Throwing parts in one after another and hoping the problem goes away is no way to do a diagnosis..

Reply to
Robert Hancock

I tend to agree with that. But being it's a '97 it's an OBD-II system that should give a little more detail than what he's getting.

The fact that it ran fine for 10 months seems to point to something here. Not sure what though.

Reply to
COTTP

My coworker had the same problem with his 99 F150. I don't know if it applies to you but he said it was solved by cleaning out a carbon clogged metal tube connected to the EGR. I didn't see it myself so I don't know what tube it was, but I know he had it to the dealer twice for an EGR valve and the light would come back on days later. Each time it would give an EGR code but had no noticable performace issue.

Reply to
TOLYN9

Have you tried a new air filter? That fixed a check engine light problem for me on a late-90's Ford pickup (6-cyl engine). Even if it doesn't cure the problem it is not wasted money.

Reply to
Bob M.

Without being able to look at the datastream it's gonna be tough.. the EGR system works by the computer sending a PWM signal to the vacuum solenoid to open the EGR valve. The tube feeding the EGR valve from the exhaust has a orifice in it. Flow through the tube causes a pressure drop across the orifice. The DPFE sensor measures that pressure drop and tells the computer how much flow the EGR system is seeing.

If you can view the datastream you can test the various system components. If all parts (EGR valve, DPFE sensor and vacuum solenoid) are known good then I would look at leaking vacuum lines to the DPFE sensor, clogged EGR tube or EGR system passageways. Also possible would be electrical issues.

What's happening is that the computer is calling for EGR flow, but doesn't 'see' any flow registering with the DPFE sensor. Could be any number of reasons.

(just worked on a 97 Taurus, same code description)

Regards,

Jim

Reply to
Jim

Check your tubes from the EGR valve for carbon deposites or blockages.

Reply to
Lewis11561

I agree with Robert..

My advice would be to take it to a dealer and pay to have them diagnose the problem. They'll probably charge you about 2 hours of labor.

If I were working on it, I'd check to see what code it set.. Then I'd look for the obvious (a dead rat in the air cleaner?), stick a vacuum gauge on the intake manifold, look at the signal going from the EGR to the computer on an oscilloscope, and then stick a 5-gas analyzer on it. And then try to draw some conclusions. The scan tool merely points in a direction.

Scan tools can also be deceptive. Because you retrieved a code, doesn't mean you got the full story. The manufacturers are required to provide emissions related codes. They are not required to provide manufacturer specific codes which might help you, but may only available on the manufacturers own system (e.g. GM Tech 2, Honda PGM, etc).. Your truck could be throwing 5 codes, 1 you see and 4 you don't. The manufacturer's system would tell you, Autozone's Generic OBDII might not.

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Reply to
Barry S.

Update!! I removed the throttle body to check the passageways in the upper part of the intake manifold. They were plugged solid! I cleaned them out, replaced everything and reset light, and knock on wood, I think its fixed. Thanks guys for the help!

Reply to
richard davico

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